The ability to produce type I interferons determines susceptibility to RSV infection and wheeze. Spann and colleagues show that epithelial cells from wheezy infants produce lower amounts of IFN-β in response to RSV than normal infants. In second passages of both nasal and tracheal epithelial cell cultures there was a lack of RSV-induced IFN-β in wheezy or atopic children.

There was a high correlation between IFN-β production by nasal and tracheal cells. RSV replication in nasal epithelial cells was approximately 5–10-fold higher in cells from wheezy infants than from normal infants. This study suggests that RSV bronchiolitis and subsequent wheeze may be caused by a pre-existent epithelial inability to mount an anti-viral immune response.